Selector switch



April 29, 1941. c. N.-HICKMAN SELECTOR SWITCH Filed July 9, 1938 3 Shets-Sheet 1 FIG, I

l/ /Jy 8 w 6 I n b l- 4 w M y 5 2 2 El 7 T/ ,z 7 5 4 I m \J m INVENTOR C/VL H/CKMAN ATTORNEY April 29, 1941. Q N, HlCKMAN 2,240,039

SELECTOR .SWITCH .Filed July 9, 1938 3 Sheets-Sheet 2 lNl ENTOR By 6. NZ H/CKMAN ATTORNEY April 1941 c. N. HICKMAN 2,240,039

SELECTOR SWITCH Filed July 9, 1938 3 Sheets-Sheet 3 FIG. 7

lNVENTOR (IN. H/C/(MAN aw. M

ATTORNEY has Patented Apr. 29, 194i SELECTOR SWITCH Clarence N. Hickman, Jackson Heights, N. Y., al-

slgnor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 9, 1938, Serial No. 218,335

11 Claims. (01. 179-2753) This invention relates to selector switches applicable for use in machine switching telephone systems and more particularly to switches of the terminal hunting type having access 'to large groups of line or trunk terminals.

In machine switching telephone systems due to the cost of the switching equipment, it is essential that all equipment be used with the utmost efficiency'since if the equipment is slow in operation a larger amount of equipment must be installed to handle peak loads than would be the case if equipment of a faster operating type were available. switches have been proposed which are capable of operation at very high terminal hunting speeds. Such switches have been provided with brush sets which are traversed in either of two directions over the terminals of panel banks by tape belts, one switch of this general type, disclosed in Patent 2,123,228, granted July 12, 1938,

for driving the tape belt which may be clutched to two oppositely rotating power shafts by magnetic clutches associated with the driving pulleys. A further switch of this type is disclosed in Patent 2,123,229, granted July 12, 1938, to W. W. Carpenter and R. F. Mallina, in which the belt is driven by a reversible alternating current motor individual to the switch and geared to one of the pulleys over which the belt runs. For arresting the movement of the brush carriage when a marked set of bank terminals is encountered by the brush set each of these switches een provided with a magnetically operated brake which cooperates with the tape belt.

Since a switch of this type travels at a very high terminal hunting speed, the brush set may overrun a marked terminal set and therefore provision has beenmade for returning the brush set to the marked terminal set in that case. However, if the return movement should be too rapid, the brush set may overrun the terminal set in its return movement. It is, therefore, the object of the present invention to provide a driving means for the tape belt which is capable of smoothly accelerating the movement of thebrush carriage at a relatively slow speed but also capable of driving the brush carriage at a high speed when once the period of acceleration has been passed and to provide efiicient means for arresting the movement of the brush carriage. In accordance with the present invention, this object is attained by providing a pneumatically operated motor for driving the tape belt of each switch unit of the sixty units mounted on the Heretofore, selector to W. W. Carpenter, is provided with two pulleys two sides of a switch frame. The switch unit cooperates with two panel type banks of terminals mounted on the frame side by side, each bank being provided with one hundred sets of vertically disposed multiple terminal strips, each of which strips has multiples for accessibility from thirty switch units on each side of the banks. By the provision of the two banks of one hundred terminal sets, two hundred lines, trunks or links may be terminated thereon.

Each switch unit'is mounted horizontally on the frame in front of a horizontal row of two hundred terminal sets of the two banks and comprises a single brush set of three or more brushes mounted on a light carriage slidable on a tubular guide rod secured at its ends to brackets attached to the vertical end uprights of the frame. The brush set is'traversed along the guide rod by two steel tapes which run over two pulleys or flanged drums mounted for free rotation on the end brackets. One end of each tape is secured to the brush carriage by a coiled spring which springs function to tension the tapes and to act as shock absorbers when the movement of the tapes is abruptly arrested. The other ends of the tapes are threaded through slots in the ends of a cylinder extending parallel to the guide rod and are attached to a piston slidabl within the cylinder.

For controlling the movement of the piston within the cylinder in either direction whereby the brush set may be traversed by the tapes in either direction over the sets of bank terminals with which the brush set is associated, the cylinder is provided at each end with a magnetically controlled air valve. Each air valve comprises an electromagnet having an air duct extending axially through its core, a valve chamber com- 'municating with the air duct, with the end of .reservoir duct at each end of the cylinder is closed and air under atmospheric pressure is admitted through the core ducts to the cylinder on either side of the piston thereby holding the piston stationary. If, however, one valve magnet, for example the magnet associated with the right end of the cylinder is energized, the pressure on the right side of the piston is reduced by suction through the reservoir duct and atmospheric pressure applied to the left side of the piston through the core duct of the magnet valve associated with the left end of the cylinder will drive the piston toward the right end of the cylinder thereby moving the brush set secured to the tape toward the left. If, however, the valve magnet associated with the left end of the cylinder were energized, a reverse movement of the piston toward the left and a movement of the brush set toward the right would result.

In order to delay the return movement of the brush set should it overrun a marked terminal set in its hunting movement the piston is made hollow and is provided with an interior valve seat in each end thereof with which a valve ball cooperates. When for example suction is applied to the left side of the piston to move the brush set toward the right in its initial hunting movement, the ball is first sucked against the left valve seat'in the piston and until it engages the valve seat the force exerted on the right side of the piston is small due to the passage of air around the ball. As soon, however, as the ball seats, the piston will accelerate rapidly. When the brush set overruns the marked terminal set and the control circuit of the switch causes the deenergization of the left valve magnet and the energization of theright valve magnet to remove suction from the left side of the piston and to apply suction to the right side of the piston, the ball in the piston must first be sucked to the right valve seat before the piston will become effective to start the return movement of the brush set to ward the left thereby keeping the acceleration of the return movement low until the brush set has stopped on the marked terminal set.

The movement of the brush set may be arrested when the brush set encounters a marked terminal set by a magnetically operated brake 1 cooperating with the tape or the brake may be mieumatically operated. In accordance with one embodiment of the invention, the brake shoe for engagement with the tape is attached to a pivoted brake lever one end of which is attached to a spring which normally forces the brake shoe against the tape and the other end of which is attached to a flexible diaphragm. The diaphragm closes one end of ,aevalve chain-- ber which is connected by one duct extending through the core of a valve magnet to the atmosphere and by a suction duct to the main air reservoir. A steel ball is positioned in the chamber which normally closes the suction duct and opens the core duct whereby atmospheric pressure is applied to both surfaces of the dia* phragm. To release the brake the valve magnet is energized to attract the ball, thereby closing the core duct and opening the suction duct whereby the pressure against the inner surface of the diaphragm is lowered permitting the at mospheric pressure on the outer surface of the diaphram to flex the diaphram inwardly and move the brake lever against spring tension thereby removing the brake shoe from the tape.

In accordance with a further embodiment of the invention, the magnetically controlled brake valve is eliminated by connecting the diaphragm chamber by a duct connected to both ends of the motor cylinder through ball valves. When brake shoe from the tape.

brake mechanism in the piston of the motor.

To accomplish .this the piston is provided with a duct extending longitudinally therethrough and with a flexible tubular outer wall which in normally pressed into engagement with the inner wall of the cylinder by a coiled spring positioned within the piston. The flexible tube thus serves as a friction brake. Each end of the duct through the piston is provided with a valve seat with which a valve ball cooperates. When suction is applied to either end of the piston, the balls both move toward the end of the piston to which suction is applied, one ball opening the valve at that end and the other ball closing the valve at the other end whereby the suction is effective to collapse the thin side walls of the flexible tube against the pressure of the spring sufficiently to remove the braking action thereof with the wall of the cylinder.

For a more complete understanding of the invention and the mode of its operation, reference may be had to the following detailed.description taken in connection with the accompanying drawings in which:

Fig. 1 is a partial top plan view of a switch frame showing two switch units embodying the invention mounted thereon;

Fig. 2 shows the brake mechanism and a partial cross-sectional view of one end of the motor cylinder and the magnetically operated valve associated therewith;

Fig. 3 is a cross-sectional view of the other end of the motor cylinder and the magnetically operated valve associated therewith;

Fig. 6 is an end view of the motor piston shown in Fig. 5;

Fig. 7 shows in partial cross-section a pneumatically operated brake mechanism;

Fig. 8 shows in partial. cross-section a further embodiment of a pneumatically operated brake mechanism;

Fig. 9 is a cross-sectional disclosure of a pneumatically controlled brake mechanism incorporated in the motor piston; and

Fig. 10 is a circuit diagram showing the manner in which the magnetically operated valves of the switch, brushes normailying switch are electrically connected.

Referring now to the drawings, the invention will be described in more detail. The switch frame on which the switch units are mounted may be of the general type disclosed in the patent of W. W. Carpenter et a1. hereinbefore referred to and comprises two channel shaped uprights 2 and 3 joined at their upper ends by the strap i welded or otherwise secured thereto and similar uprights 6 and I also joined by a strap 8. The upper ends of the uprights 2 and 3 are joined to the upper ends of uprights E and 1 by the angle bar III which is welded or otherwise secured to the flanges of the uprights,

type disclosed for example in Patent 1,127,741,

granted February 9, 1915, to A. F. Dixon and comprises two vertical side members l3 and I4 between which one hundred sets of multiple terminal strips and separator strips are clamped. The banks are secured to the upper angle bar l8 and to the lower angle bar of the frame by straps i5 and I6 which are attached to theangle bars by screws and to the side members l3 and I4 of the banks by bolts |1. Each terminal strip is provided with thirty multiple terminals extending outwardly on each side thereof and with a soldering terminal at each end whereby accessibility is afforded to sixty selector switch units thirty on each side of the banks. The terminal strips are arranged in sets of four to which the tip, ring, sleeve and metering leads of a subscribers line may be connected, although in some instances, as for example when the switch frame is to be used for other purposes, each set might comprise three terminal strips. The corresponding sets of multiple terminals on the several sets of strips in both banks are aligned horizontally and individualized to different selector switch units.

For supporting each selector switch unit on the switch frame in proper relationship to the horizontal row of bank terminal sets'to which-it is individualized, two brackets I8 and |9 are provided, the supporting brackets of the switch units on the front of the frame being secured to the outside flanges of the upright channel members 3 and 1 and the switch units on the rear of the frame being secured to the outside flanges of the upright channel members 2 and 6. Each bracket is in general channel shaped having a horizontal web 20, an outer flange by which it is attached to a vertical upright of the switch frame and an upwardly extending flange 2|.

Secured to the flange 2| of bracket I8 as by screws or welding is an L-shaped member 22 and similarly secured to the flange 2| of bracket H! is an L-shaped member 23, said members 22 and 23 serving to support the tubular guide rod 24 and the pneumatic driving motor 25 of the switch unit in parallel relation to the face of the terminal banks. The ends of the tubular guide rod 24 are seated in bushings 26 of insulating material which are secured to the members 22 and 23 in any' desired manner whereby the guide rod is electrically insulated from the switch frame.

Slidable on the guide rod 24 of each switch unit is a brush carriage 21 having a rectangular frame 28 as most clearly disclosed in Fig. 4, the

ends of which are provided with bushings 29 which slidably embrace the guide rod. Insulatedly secured to the frame 28 by screws 30 are brush springs 3| to 34, inclusive, each provided with a contact shoe 35. These brushes serve as sleeve, tip, ring and metering brushes, respectively, for cooperation with sets of terminals on the terminal banks or if no meter control is necessary and the bank terminal sets having only tip, ring and sleeve terminals, the outer two of the brushes may be electrically connected together. For connecting the brush springs to external circuits, the ring brush 33 is connected to a terminal positioned on the bushing 26 attached to the member 23 by a flexible insulated conductor 36 coiled around the guide rod 24 on one side of the brush carriage, the tip brush 32 is 'connected by a second flexible conductor 31 coiled around the guide rod 24 on the other side of'the brush carriage and extending through the tubular guide rod to a second terminal positioned on the bushing 26, the sleeve brush 3| is electrically connected through the brush carriage frame 28 and the spring 38 attached thereto which slides on the guide rod to an external conductor connected to the end of the guide rod, and when a metering control is necessary the fourth or metering brush 34 is connected by a third flexible conductor coiled around the guide rod 24 in the same manner'as conductor 36.

For traversing the brush carriage 21 along the guide rod 24 a pneumatic motor 25 is provided. This motor comprises a cylinder 39 preferably made of thin squaretubing having its ends closed by plugs 40 of hard rubber or other suitable material. To support the cylinder parallel to the guide rod a plate 4| is brazed or otherwise secured to a side wall of the cylinder at each end thereof which plates are secured to the members 22 and 23 by screws 42. Slidably positioned in the cylinder is a piston 43 preferably of molded hard rubber, each end of which is provided with a ball 44 molded therein to which the ends of two driving tapes 45 and 46 are connected.

The tape 45 extends through a slot in the plug 40 in the left end of the cylinder, thence over an idler pulley or flanged drum 41 journaled on stub shaft 48 secured on the web 28 of the end bracket 8 and is secured at its other end through a coiled spring 48 to one end of the brush carriage 21. The tape 46 similarly extends through a slot in the plug 48 in the right end of the cylinder over an idler pulley 58 journaled on a stub shaft 5| secured on the web 20 of end bracket i9 and is secured at its other end through a coiled spring 52 to the other end of the brush carriage. The coiled springs 49 and 52 serve the dual purpose of tensioning the tapes andabsorbing the shock incident to starting and stopping the brush carriage. ,7

The piston 43 is provided as shown in Fig. 5 with a bore 53 extending axially therethrough one end of the bore being reduced in diameter at its point of emergence through the end wall of the piston to form a valve seat 54. The other end of the bore is threaded to receive a plug 55 having an opening'therethrough and formed on its inner end with a valve seat 56. Freely movable within the central bore is a valve ball 51 which cooperates with the ball seats for a purpose-to be later described. i

Each end of the cylinder 39 is provided with a valve assembly. The valve assembly on the left end of the cylinder, as disclosed in Fig. 3, comprises a base plate 58 soldered or otherwise secured to the outer front wall of the cylinder and having an opening therein aligned with an opening in the wall of the cylinder, a plate 59 having a tubular valve chamber 68 struck up therefrom or secured thereto by solder or other suitable means, a clamping plate 6| having a hole therein through which the valve chamber 68 extends and an L-shaped heel-piece 62. The valve chamber plate 59 is clamped to the base plate 58 with the valve chamber aligned with the openings through the plate 58 and the wall of the cylinder the outer end of which is seated in an opening in a side wall of the valve chamber 00. The core has an air duct extending therethrou'gh which is provided on the end communicating with the valve chamber with a valve seat 01. An electro- -magnet coil'tOR is positioned on the core between the valve chamber 00 and the heel-piece 82, the terminals of which are connected to terminal lugs 60 insulatediy secured to the heel-piece 82 by screws 10. The screws I0 also serve to aid in securing the heel-piece 02 in position. The outer end of the valve chamber 60 is closed by a plug II through which an exhaust air duct I! having a valve seat It on its inner end extends. Positioned within the valve chamber and cooperating with the valve seats 61 and I3, is a steel valve ball I4 which upon the energization of the magnet coil 08 is attracted from a position in which it normally rests on the valve seat I0 closing the air duct 12 into a position on the valve sat 01 for closing the air duct 06 through the magnet core. The air duct I2 is connected by flexible rubber tube II with a branch It oi! the supply pipe 11. The supply pipe 11 is supported by ,clamps I0 on the upright I and is connected to an air reservoir (not shown) which is connected to a suitable exhaust pump.

The valve assembly associated with the right end 01 the cylinder 30 is similarly constructed, the exhaust air duct I2 thereot being connected by rubber tubing I9, pipe 80, and rubber tubing II to a branch 02 oi. the supply pipe 03. The supply pipe 00 is supported by clamps 04 on the upright I and is connected to the air reservoir.

Associated with each switch unit adjacent to the right endv oi! the driving motor cylinder is a magnetically controlled brake which cooperates with the driving tape 46. The brake mechanism comprises an end support 05 which is secured to the member by screws 86 which extend through the support It and spacing sleeves 01 and engage in threaded openings in the member 20. Secured to the inner face of the support 05 is; an L-shaped return pole-piece 88 through which and through the support 85 the magnet core 00 is threaded. The threaded end of the core It provided with a hexagonal nut portion by means of which the core may be turned in the threaded opening or the support" for adjusting the air gap between the free end 0! the core and the magnet armature. For clamping the core in its adjusted position, the lock-nut 00 is provided. A magnet coil OI is supported on the free end of the core 00.

Secured to the free end of the pole-piece 80 by screws is a bracket 02 provided with ears between which the magnet armature 03 is pivoted. One end of the armature overlies the end of polepiece 00 and the end of magnet core 09 and is provided near its pivot with a brake shoe 04 which cooperates with the brake shoe 05 attached to the meinber 23. The coiled spring 06, one end 0! which is secured to the outer end or the armature Q3 and the other end of which is securedto the tensioning screw 91 is provided for normally retracting the armature 93 and for Xorcing the brake shoe 04 carried thereby toward the stationary brake shoe 0! to clamp the tape ll therebetween. The position or the brake shoe 8| with respect to the pivot point oi. the armature, to the point of attachment of spring 90 to the armature and to the end of the armature which overlies the end of core 09 is so chosen that the motion of the brake shoe is very slight in the order ot a few thousandths of an inch but that the braking eiiect applied thereto by the spring 86 is quite large. Since, however, the end of the armature which overlies the magnet core has considerable leverage, the magnet coil 9| when energized is quickly able to overcome the spring 86 to disengage the brake shoe 9! from the tape 40. To enable the adjustment of the tension in spring 96, the screw 01 to which the outer end of the spring is connected is caused to slide in the U-shaped extension or the supporting plate 05 by the rotation 01 the knurled nut threaded upon the outer end of the screw.

Each switch unit is also provided with a normalling switch disclosed most clearly in Fig. 4, comprising a spring pile-up 09 insulatedly secured to the front wall of the motor cylinder 39 and an operating member I00 pivotally secured to the upper wall of the cylinder at a point opposite the mid-point between the terminal banks II and I2 of the switch frame. The spring pile-up comprises a middle or active spring IM and passive springs I02 and I03 mounted on either side thereof. The springs are all provided at one end with soldering lug extensions and are clamped near that end to the front wall of the cylinder 39 by screws I04 which extend through the outer clamping plate I05 through the springs and the insulating separators I06 into threaded openings in the cylinder wall. The springs are insulated from each other and from the cylinder 30 by the insulating separators I06 and. from the screws I04 by any suitable means such as fibre sleeves surrounding the screws I04.

The passive springs I02 and I03 are held in such a position as to be normally out of engagement with the middle spring IN by tangs extending upwardly therefrom which are seated in holes in the comb bar I01 of insulating material, secured to the upper wall of the cylinder 39 by screws I08.

The operating member I00 is triangular in shape and is pivoted to the upper face of the cylinder 39 by a screw I09. The tip of the member is provided with a roller H0 of insulating material which cooperates with the cam extension III oi. the spring IOI. Pivoted to the wide end of the member I00 are two fingers II! and I I3, the outer ends of which are normally engaged against stop pins Ill and H5, secured to the member I00, by the coiled spring H6 the ends of which are secured to the ends of the fingers. When the brush carriage 21 is in its normal position at the mid-point between the terminal banks as disclosed in the upper portion of Fig. 1 and also in Fig. 4, the insulated stud Ill attached to the brush carriage is engaged between the ends of fingers III and H3 and the member I00 is held in its neutral position.

Should the brush carriage move toward the right as viewed in .Fig. 4 and engage the stud II! with the finger Ill, due to the engagement of the outer end of the finger with the stop pin H5, the movement of the brush carriage will rotate the member I00 in a clockwise direction, thereby moving the roller IIO away from the extension III on spring IOI thereby permitting the spring to move into engagement with spring I02 preparatory to restoring the brush carriage toward the left into its normal position following the termination of the connection. When thereafter the brush carriage is returned toward the left, the stud H'l will engage the end of finger I I3 and snap over it since the finger will at this time pivot away from its stop pin H5. The stud l H as it continues its movement toward the left will then engage the inner edge of finger H2 and since this finger is held from pivoting by its stop pin H4, the pressure of stud H1 against the end of finger I it, will cause the member I36 to rotate around its pivot I89 in a counter-clockwise direction thereby causing the disengagement of spring iOl from spring I02 to arrest the return movement of the brush carriage.

Should the brush carriage be moved initially toward the left and engage stud ill with the inner edge of finger H2, due to the engagement of the outer end of the finger with the stop pin H4, the member tilt will be rotated in a counterclockwise direction, thereby moving the roller I into engagement with the cam section ill of spring Illl to engage the spring with spring Hi3 preparatory to restoring the brush carriage towards the right into its normal position. When thereafter the brush carriage is returned toward the right, the stud ill will engage the end of finger l I2 and snap over it into engagement with the inner edge of finger H3 and since this finger is held from pivoting by its stop pin H5, the member lllll will be rotated in a clockwise direction thereby causing the disengagement of the spring llll from spring IE3 to arrest the return movement of the brush carriage.

For enabling the connection of control conductors to various elements of the switch unit connecting blocks I I8 are provided individual to the switch unit which are attached by screws to the end brackets I8 and I9.

Considering now the manner in which the switch unit functions and referring particularly to the diagram of Fig. 10, it will be assumed that a line or trunk terminating in the left bank H on the switch frame is placed in a calling condition and that a control circuit (not shown) but of the type disclosed in the patent of W. W. Carpenter hereinbefore referred to, connects operating battery to terminal H9 of connecting block H8 and ground to terminals I20 and I 2|. The magnet coil 68L of the valve at the right end of the motor cylinder 39 and the brake magnet coil 9| are thereby energized, the coil 68L causing the attraction of the steel ball I4 associated therewith against the valve seat 61, as shown in Fig. 2, to close the air duct 66 extending through the core 65 and away from the valve seat 13 to open the duct I2 connected to the evacuated air reservoir. At this time the ball 14 of the valve at the left end of the motor cylinder 39, as most clearly disclosed in Fig. 3, is held by suction from the air reservoir against the valve seat 13 thereby closing the suction duct 12 and opening the duct 66 through the core 65 since the magnet coil 68B. is at the time unenergized. Brake magnet coil 9| upon energizing removes the brake shoe 94 from engagement with the tape 46, thereby freeing the tape and the brush carriage 21 to which it is attached for movement.

With the suction duct at the rightend of the cylinder opened and the core duct 66 closed and the core duct 66 at the left end of the cylinder open, suction is applied to the right end of the cylinder 39 and to the right end of the piston 43 therein and air under atmospheric pressure enters through the duct 66 at the left end of the cylinder into the left end of the cylinder against the left end of piston 43. In response to thedifference of air pressure applied to the ends of the piston, air at first passes through the duct 53 in the piston, disclosed in Fig. 5, around the valve ball 61 but almost immediately thereafter forces the valve ball 51 into engagement with the valve seat 56 in the right end wall of the piston, whereby the air pressure then becomes fully effective to move the piston 43 toward the right and by the tape 46 attached to the left end of the piston to move the brush carriage 21 toward the left along its guide rod 24 thereby moving the brushes of the brush set over the horizontal, rows of terminals of the left terminal bank ll allocated to the switch unit.

As soon as the brush carriage leaves its normal position, the springs IM and i533 of the normalling switch are engaged as previously de-= scribed preparatory to returning the brush carriage to its normal position and when the sleeve brush 3| of the brush set engages the sleeve ter minal of the calling line, a test circuit is establlshed therefrom over terminal E22 of the connecting block M8 to the. control circuit (not shown) which is effective to cause the deenergization of magnets 38L and 3!. Magnet 8! upon deenergizing reapplies the brake shoe 94 to the tape 46 to arrest further movement of the brush carriage and magnet 68L upon deenergizing releases the ball I4 from the valve seat 61 oi. the valve at the right end of the cylinder whereupon the ball is sucked against the valve seat 13 of the suction duct I2. With the balls of both valves now closing the suction ducts 12 and opening the core ducts 66. the pressure on both sides of the piston 43 becomes equalized at atmospheric pressure and the piston has no further tendency to move within the cylinder.

If due to its speed the brush carriage has moved in its hunting movement to carry the sleeve brush 3| beyond the marked bank terminal, the control circuit will become effective as described in the patent of W. W. Carpenter to cause the brush carriage to be moved toward the right to return the sleeve brush 3| to the marked terminal. To accomplish this, the operating circuits of valve magnets 68R and brake magnet 9| are established over terminals I23 and I2| of the connecting block H8. With magnet 9| energized, the brake shoe 94 is withdrawn from the tape 46 to free the brush carriage for movement and with valve magnet 68R energized and valve magnet 68L deenergized, suction is applied to the left end of the cylinder 39 and air under atmospheric pressure is admitted to the right end of the cylinder.

Due to the difference in pressure applied to the opposite ends of the piston 43, air at first passes through the duct 53 in the piston around the valve ball 51 but the piston is, however, forced slowly towards the left and by the tape 46 connected to the-right end thereof moves the brush carriage towards the right. As soon as the ball 51 becomes seated on the ball seat 54 in the left end wall of the piston, the full difference of pressure applied to the opposite ends of the piston be- I comes effective to accelerate the movement of the piston toward the left. The valve ball 51. is thus effective to retard the acceleration of the brush set so that it will not cause the sleeve brush 3| to overrun the marked terminal on its return movement. When the marked terminal is again encountered, the test circuit from brush 3| over terminal I22 is reestablished resulting in the deenergization of magnets 33R and 3| to arrest the movement of the brush set.

When the established connection is no longer required, the control circuit completes the circuit of magnet 3| over terminals I I3 and HI and with the springs IN and I03 of the normalling switch now engaged, completes the circuit of valve magnet 63R over terminals H3 and I24, whereupon the brush carriage is returned toward the right to its normal position, in which position the springs IM and I03 disengage to open the circuit of magnet 63R. The circuit 01' magnet BI is also opened at this time whereupon the return movement of the brush carriage is arrested.

It the calling line had been located in the right terminal bank I2, the control circuit would have established the circuits oi brake magnet 3| and oi valve magnet R. to advance the brush set in an initial hunting movement over the right terminal bank, the brush carriage being returned toward the left in the event the sleeve brush 3| overran the marked terminal by the deenergization 01' magnets 63R and 3| and the subsequent energization oi magnet 3| and valve magnet 63L. In this case, the initial movement of the brush carriage to the right operates the normalling switch to engage contact springs I and I02 preparatory to controlling the reoperation 01' magnets 3| and 68L for returning the brush carriage to its normal position upon the release of the connection.

To reduce the amount of current required to move the brake shoe 34 from the tape at the time the brush carriage is being advanced, the

modified brake mechanism disclosed in Fig. 7

may be used in place of the mechanism shown in Fig. 2. In accordance with this modification. a support I 01. magnetic material is provided which is secured to the member 23 by screws I26 extending through the support I25 and through spacing sleeves I21 into threaded holes in member 23. This support is provided on its inner face with a pedestal I23 on the outer end of which the brake lever I23 is pivoted and with a cylindrical portion I30 serving as a diaphragm chamber and on its outer face with a cylindrical valve chamber Ill communicating with the diaphragm chamber I30. The diaphragm chamber I30 is closed by a concentrically corrugated diaphragm I32 which is held in position 'by a clamping ring I33 secured to the edge of the chamber I30 by screws I34. The diaphragm is connected to one end of the brake lever I23 by a link I which is riveted or otherwise secured to the center of the diaphragm. Secured to the lever I23 between the end connected to the diaphragm and the pivot point oi the lever and near the pivot point is a brake shoe 34 which cooperates with the brake shoe 35 attached to the member 23. The coiled spring 36, one end oi which is secured to the other end of lever I23 and the other end of which is secured to the tensioning screw 31, is provided for normally holding'the brake lever I23 in such a position as to force the brake shoe 34 toward the shoe 35 to clamp the tape 46 therebetween. To enable the adjustment of the tension 01' spring 36, the screw 3-! to which the outer end of the spring, is connected is caused to slide in the U-shaped extension I36 of support I25 by I the magnet core I33 is positioned. The core extends parallel to the race of the support I25 and is attached at one of its ends to the heelpiece and is provided at its other end with a shouldered portion which is seated in an opening in the side wall of the valve chamber I3I. The core is surrounded by a magnet coil I40 and is provided with an air duct I H extending axially therethrough. In the side wall 01 the valve chamber. opposite the core dust I and aligned therewith is an opening in which is secured a branch I42 0! an air duct, the second branch I2 0! which is connected to the valve chamber 60 of the motor cylinder and a third branch I43 oi which is connected by the rubber tubing III to a branch 32 of the supply pipe 83 as shown in Fig. 2. Positioned within the valve chamber I3I and supported on the end wall thereof is a steel valve ball I44 which is normally held by suction against the valve seat I45 formed on the end of the duct I42 but which is attractable to the end of the core I33 against the valve seat I43 i'ormed in the end of the core ductwhen the magnet 'coil I40 is energized.

This brake mechanism functions in the i'ollowing manner: with the magnet coil I40 deenergized the bail I44 is held by suction on the valve seat I45 thereby closing the suction duct and opening the core duct, whereby air under atmospheric pressure is applied throughthe core duct, valve chamber and diaphragm chamber to one face oi the diaphragm I32, and since the other face of the diaphragm is exposed to the atmosphere, the diaphragm remains unflexed and the spring 36 holds the brake shoe 34 against the tape 46. When, however, the brake magnet coil I40 is energized together with one of the motor valve magnets 63R or 68L to initiate the operation of the brush carriage, magnet I40 upon energizing attracts the ball I44 to the valve seat I46 in the core duct I to close the core duct and to open the suction duct I42 whereby the air pressure in the diaphragm chamber is reduced below atmospheric pressure. The pressure on the outside or the diaphragm now being greater than the pressure on the inside thereoi flexes the diaphragm into .the chamber I 30 and through the link I35 swings the brake lever I29 against the tension of spring 36 to remove the brake shoe 34 from the tape 46 whereby the tape and the brush carriage to which it is attached may be moved by the motor in either-of its directions of movement dependent upon which one of the valve magnets 681?. or 60L is at the time energized.

A further modification oi the pneumatically operated :brake mechanism is disclosed in Fig. 8 which is similar to that disclosed in Fig. 7 except that the control magnet and associated valve ball are omitted. According to this modification the suction duct I42 connected to the chamber I3l is connected by rubber tubing I41 to a duct I43 having two branches I43, one of which is shown, connected to auxiliary valves associated with the two ends of the motor cylinder 33. Each auxiliary valve comprises a flanged tubular chamber I50, the flanged portion of which is clamped by screws I52 between the clamping ring I'5I and the plate H which supports the end of the motor cylinder 39, plug I53 which serves to close the outer end of the chamber and through which the branch I43 of the duct I48 extends and a valve ball I54. The plate M is provided with an opening or the same diameter as the inside diameter of the chamber I and a small opening I55 is provided in the wall of the .cylinder 39 for permitting the passage oi air between thechamber and the cylinder. Normally the ball I54 of the valve at each end of the cylinder rests in the position shown in Fig. 8, but not closing the openings I55 through the cylinder wall.

When, for example, the valve magnet 58L is energized for the purpose of moving the brush carriage to the left and the ball 14 is moved from the valve seat I3 on the end of the suction duct I2, to close the core duct 66, suction is applied to the right side of the 'motor piston and through the opening I55, chamber I50, ducts I48 and I42 to the diaphragm chamber I30 of the brake mechanism whereby the diaphragm I32 becomes flexed inwardly to move the brake shoe 94 from engagement with the tape. The suction applied to the duct I48'is also effective to suck the ball Hit in the valve chamber I50 at the left end of the motor cylinder into engagement with the valve seat on the end of branch 9 of the duct M8 to prevent suction from being applied to the left end of the cylinder. With air. at atmospheric pressure applied to-the cylinder on the left end oi the piston, the piston is therefore drawn toward the right end of the cylinder in the manner previously described.

Should the valve magnet ddR at the left end oi. the cylinder be energized with the magnet tall at the right end of the cylinder deenergized, suction will be applied to the left end of the cylinder and through the valve chamber the at the left end of the cylinder to the duct its thereby causing the brake shoe @d to he disengaged from the tape as previously described and causing the ball to close the branch it?) of the duct M8 at the right end of the cylinder to prevent suction from being applied to the right end of the cylinder. The piston will in this case he forced toward the left end'oi the cylinder thereby moving the brush set toward the right. It will thus be apparent that whenever either valve magnet is energized the brake shoe @flwill become disengaged irom the tape to enable the tape and brush set to be advanced by the pneumatic motor.

As a further modification of this invention, the brake mechanism such as disclosed in Figs. 2, l and 8 may be entirely eliminated by incorporating a brake in the motor piston as shown in Fig. 9. in accordance with this modification the piston comprises a body portion 355% having flanged ends, an axial duct is? extending through the body portion and an opening through the body of the piston at right angles to the duct iii? and communicating therewith. Each end of the duct is enlarged indiarneter and provided with a valve seat 95%). The ends of the piston are closed-by discs i 59 secured thereto in any desired manner to which bails M are secured and which also serve as a means for retaining the valve balls 469 within the enlarged portions of the duct Each of the discs is provided with an aperture r52 for the admission of air to the inside of the piston. Surrounding the body portion and making an air tight contact with the flanged ends thereof is a sleeve 863 of thin sheet metal or other suitable flexible material which is normally flexed outwardly by. the coiled spring its located within the opening H58 in the body of the piston.

Withthe piston in position in the cylinder,'the

spring its normally flexes the sleeve @363 into engagement with the inside walls of the cylinder with sufiic'ient pressure to frictionally hold the piston against movement in the cylinder. When,

however, suction is applied to either end of the piston, the ball I6I at the opposite end 01' the piston will be forced against its seat I59 thereby closing the opposite end of the duct I51 whereby the suction will be effective to collapse the sleeve I63 sufllciently to reduce its frictional engagement with the inner walls of the cylinder, thus freeing the piston for movement within the cylinder. With suction thus applied to one end of the piston and atmospheric pressure applied to its opposite end now closed by the valve ball I5I, the piston is forced along the cylinder 39. As soon, however, as the suction is removed, the spring I64 becomes effective to again flex the sleeve I53 into frictional engagement with the inner walls of the cylinder thereby serving'as a brakev to arrest the movement of the piston and the movement of the'brush carriage controlled thereby.

What is claimed is:

1. In a selector switch having a bank of terminals and a brush set cooperating therewith, a

brush carriage upon which said brush set is mounted, a belt traversible in either of two directions for moving said brush carriage to traverse said brush set in either direction across said bank, supporting pulleys for said belt, a pneumatic motor for traversing said belt operable by air at atmospheric pressure and a reservoir of air under less than atmospheric pressure,-

said motor comprising a cylinder through which said belt passes, a piston within said cylinder to which said belt is secured and a magnetically controlled valve associated with each end of said cylinder forconnecting either end of said cylinder with the atmosphere or with said reservoir.

2. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a pneumatic motor operable by air at atmospheric pressure for moving said brush carriage' to traverse said brush set in either direction across said bank and a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder to which said brush carriage is connected and a magnetically controlled valve associated with each end of said cylinder, each of said valves comprising a valve chamber, a'first valve seat in said chamber, a duct connecting said valve seat with the atmosphere, a second valve seat in said chamber, a second duct connecting said second valve seat with said reservoir, a valve ball for cooperating with-said valve seats and normally resting on said second valve seat to close said reservoir duct, and an elec'tromagnet operative upon its energization to move said ball to said first valve seat to open said second duct and to close said first duct.

8. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a pneumatic motor operable by air at atmospheric pressure for moving said brush carriage to traversesaid brush set in either direction across said bank and a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder to which said brush set is connected and a magnetically controlled valve associated with each end of said cylinder, each of said valves comprising a valve chamber, an electromagnethaving its core extending into said chamber and formed with a first valve seat in the end thereof, a first duct connecting said valve seat with the atmosphere, a second valve seat in said chamber, a second duct connecting said second valve seat with said reservoir, a valve ball for cooperation with said valve seats and normally resting on said second valve seat to close said reservoir duct and attractable on the energization of said electromagnet to said first valve seat to open said second duct and to close said first duct.

4. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a pneumatic motor operable by air at atmospheric pressure for moving said brush carriage to traverse said brush set in either direction over said bank and a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder connected to said brush carriage and a magnetically controlled valve associated with each end of said cylinder for connecting either end of said cylinder with the atmosphere or with said reservoir, said piston having a duct extending therethrough and a valve in said duct operable to close said duct when the air pressure on one side of said piston is reduced whereby until said duct is closed the acceleration of said piston is'delayed.

5. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a pneumatic motor operable by air at atmospheric pressure for moving said brush carriage to traverse said brush set in either direction across said bank, and a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder to which said brush carriage is connected and a magnetically controlled valve associated with each end of said cylinder for connecting either end of said cylinder with the atmosphere'or with the reservoir, said piston having a valve chamber therein provided with a valve seat on each end thereof, ducts extending from said valve seats through the end walls of said piston and a valve ball within said chamberoperable into engagement with either one of said valve seats whereby when a difierence of air pressure is established on opposite ends of said piston air is first permitted to leak through said system to delay the acceleration thereof until the difi'erence in air pressure causes said ball to become seated on one of said valve seats.

6. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a belti'or moving said brush carriage to traverse said brush set in either direction over said bank, supporting pulleys for said belt, a motor for driving said belt and a brake mecha-' nism for arresting the movement of said belt comprising a brake shoe, a spring for normally engaging said brake shoe with said belt, a pneumatic. device for retracting said brake shoe and a reservoir oi air under less than atmospheric pressure, said pneumatic device comprising a chamber aseociable with said reservoir, a diaphragm closing said chamber having one of its surfaces exposed to the atmosphere and connected to said brake shoe and a valve for controlling the connection or said chamber with said reservoir whereby atmospheric pressure acting. upon said diaphragm causes the retraction of said brake shoe.

'I. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a belt for moving said brush carriage to traverse said brush set in either direction across said bank, supporting pulleys for said belt, a motor for driving said belt and a brake mechanism for arresting the movement of said belt comprising a brake lever, a brake shoe secured to said lever, a spring for operating said lever to normally engage said brake shoe with said belt, a reservoir of air under less than atmospheric pressure and a pneumatic device for retracting said brake shoe, said devicecomprising a valve chamber, a dia-' phragm closing said chamber having the outer surface thereof exposed to atmospheric pressure and connected tosaid brake lever,an electromagnet having its core extending into said chamber and formed with a first valve seat in the end thereof, a first duct connecting said valve seat with the atmosphere, a second valve seat in said chamber, a second duct connecting said second valve seat with said reservoir, a valve ball for cooperation with said valve seats and normally resting on said second valve seat to close said reservoir duct and to open said first duct whereby both surfaces of said diaphragm are subjected to atmospheric pressure and attractable to said first valve seat to open said reservoir duct and to close said first duct whereby the pressure on the surfaces oi said diaphragm is unequalized to cause said diaphragm to flex and operate said lever to disengage said brake shoe from said belt.

8. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a belt for moving said brush carriage to traverse said brush set in either direction over said bank, supporting pulleys for said belt, a pneumatic motor for driving said belt operable by air at atmospheric pressure, a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder to which said belt is secured and a magnetically controlled valve associated with each end of said cylinder for connecting either end of said cylinder with the atmosphere or with said reservoir, a brake mechanism for arresting the movement oi said belt comprising a brake shoe, a spring for normally engaging said brake shoe with said belt and a pneumatic device for retracting said brake shoe, a duct connecting said pneumatic device with each end of said cylinder and pneumatically operated valves interposed between said duct and the ends 01' said cylinder.

9. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a pneumatic motor operable by air at atmospheric pressure for moving said brush carriage to traverse said brush set in either direction across said bank and a reservoir oi air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder connected to said brush carriage and a magnetically controlled valve associated with each end of said cylinder for connecting either end 01' said cylinder with the atmosphere or with said reservoir, said piston having a duct extending therethrough, valves in said duct operable to close said duct at the end thereof opposite to that to which suction from said reservoir is applied, a flexible sleeve surrounding said piston and a spring within said piston normally eflective to expand the sleeve into frictional engagement with the inner walls oi said cylinder whereby said piston'serves as a brake to arrest the movement or said brush car liage, said sleeve being collapsed to remove the braking eflect thereof when suction is applied to either end oi said piston.

10. In a selector switch having a bank of terminals and a brush set cooperating therewith, a brush carriage upon which said brush set is mounted, a belt for moving said brush carriage to traverse said brush set in either directionover said bank, supporting pulleys for said belt, a

pneumatic motor for driving said belt operable by air at atmospheric pressure, a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder, a piston within said cylinder to which said belt is secured and a magnetically controlled valve associated with each end of said cylinder for connecting either end of said cylinder with the atmosphere or with said reservoir, said piston having a duct-extending therethrough, valves in said duct operable to close said duct at the end thereof opposite to that to which suction from said reservoir ,is applied, a flexible sleeve surrounding said piston and a spring within said piston normally efiective to expand said sleeve into frictional engagement with the inner walls of said cylinder whereby said piston serves as a brake to arrest the movement of said belt,

said sleeve being collapsed to remove its braking effect when suction is applied to either end oi said piston.

11. In a selector switch having a bank of terminals and a brush set cooperating therewith. a brush carriage upon which said brush set is mounted, a belt for moving said brush carriage to traverse said brush set in either direction across said bank, supporting pulleys for said belt, a pneumatic motor for driving said belt operable by air at atmospheric pressure and a reservoir of air under less than atmospheric pressure, said motor comprising a cylinder having substantially closed ends through which said belt passes, a piston within said cylinder to which said belt is secured and a magnetically controlled valve associated with each end of said cylinder for connecting either end of said cylinder with the atmosphere or with said reservoir, said piston having a duct extending therethrough and a valve in said duct operable to close said duct when the air pressure on one side of said piston is reduced to delay the acceleration of said piston.

CLARENCE N. HICKMAN. 

